Software running on a processor, microprocessor, and/or processing unit to provide certain functionality often changes over time. The changes can result from the need to correct bugs, or errors, in the software files, adapt to evolving technologies, or add new features, to name a few. In particular, embedded software components hosted on mobile processing devices, for example mobile wireless devices, often include numerous software bugs that require correction. Software includes one or more files in the form of human-readable American Standard Code for Information Interchange (ASCII) plain text files or binary code. Software files can be divided into smaller units that are often referred to as modules or components.
Portable processor-based devices like mobile processing devices typically include a real-time operating system (RTOS) in which all software components of the device are linked as a single large file. Further, no file system support is typically provided in these mobile wireless devices. In addition, the single large file needs to be preloaded, or embedded, into the device using a slow communication link like a radio, infrared, or serial link.
Obstacles to updating the large files of mobile processing devices via slow communication links include the time, bandwidth, and cost associated with delivering the updated file to the device. These obstacles arise because, in many cases, the differences between the new and original versions of the executable files are more complex than the differences between their corresponding source files.
These complex differences between the new and original file versions arise in part because small changes in the source files often introduce major changes throughout the executable files. As an example, one type of change introduced in the executable files is a logical change that includes source code changes arising from source code line deletion from the original file, source code line addition to the new file, and source code line modifications. The logical changes also include data initialization changes, resource and configuration file changes, and dictionary changes.
Another type of introduced change, often referred to as a secondary change includes address changes, pointer target address changes, and changes in address offsets caused by address shifts resulting from the logical changes or code block swapping and generated by the software compiler/linker utilities.
Yet another type of introduced change includes byte-level code changes generated by the compiler/linker utilities not stemming from changes in the code logic or address shifts. For example, an instruction in the original version uses register R1, but the same instruction uses register R3 in the new version when, for example, register R1 is not available.
One typical solution to the problem of delivering large files to mobile processing devices includes the use of compression. While a number of existing compression algorithms are commonly used, often, however, even the compressed file is too large for download to a device via a slow, costly, narrowband communication link.
Another typical solution for updating files uses difference programs to generate a description of how a revised file differs from an original file. There are available difference programs that produce such difference data. However, as with compression, the difference files produced using these difference programs can sometimes be too large for efficient transfer via the associated communication protocols.
In the drawings, the same reference numbers identify identical or substantially similar elements or acts. To easily identify the discussion of any particular element or act, the most significant digit or digits in a reference number refer to the Figure number in which that element is first introduced (e.g., element 106 is first introduced and discussed with respect to FIG. 1).